Spectral study of dissolved organic matter in biosolid during the composting process using inorganic bulking agent: UV-vis, GPC, FTIR and EEM

The chemical changes of dissolved organic matter (DOM) extracted from the biosolids during 100-days composting were assessed by the means of UV-visible spectra combined gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy and excitation-emission matrix (EEM) fluorescence spectra. Pumice was used as the inorganic bulking agent to eliminate the influences of conventional organic materials on the analysis result of the biosolid samples. The results showed that the DOC/DTN (1.97-0.83) of the biosolid extract was distinctly lower than the C/N (6.88-7.84) of the biosolid sample; both low DOC/DTN ratio and poor biodegradability of the DOM had the important relation with the nitrogen loss in the biosolid composting process. After 100-days composting, SUVA254 and SUVA280 of the aqueous extract were 17.6 and 18.6 times higher than that of the raw biosolid, respectively. Both of them were proved to be the effective indices to evaluate the stability degree of the biosolid. Spectral analysis of the DOM represented significant decline of aromatic proteins, clear rising of humic acid-like organics and slight increase of fulvic acid-like materials during the active phase of composting. The formation of the larger molecules with an amount of carboxylic and aromatic structures was observed in the curing phase.